The objective of this K25 Mentored Career Development Award is to facilitate the candidate's career transition from a biostatistician to an HIV prevention scientist dedicated to promoting HIV preventive behaviors in at-risk populations. We now have efficacious biomedical interventions for combined HIV prevention (e.g. male circumcision, treatment as prevention and PrEP). However, the impact of these strategies on the epidemic is contingent on behaviors including acceptance, adherence/retention and prevention of risk compensation. My long-term goal is to conduct independent social epidemiologic research to identify and interpret individual and societal factors influencing HIV preventive behaviors, to develop statistical methods to address the analytic challenges encountered in such research, and provide leadership in the design, implementation and evaluation of interventions to promote health seeking behaviors for HIV prevention. The training and mentorship through this K25 will allow me to become well grounded in the theoretical and methodological frameworks that underlie behavioral HIV preventive interventions. Building on the mentoring expertise at the Johns Hopkins University and the research infrastructure of the Rakai Health Sciences Program (RHSP) in Uganda, the proposed mentored research seeks to identify and interpret multilevel predictors for medical male circumcision (MMC) uptake in Rakai. MMC is an important HIV prevention strategy for sub-Saharan Africa (S-SA), and its long-term population impact on the HIV epidemic depends on the pace of uptake and level of coverage in men. RHSP conducts annual HIV/STI, health and behavioral surveillance in consenting residents aged 15-49 in 50 communities through the Rakai Community Cohort Study (RCCS),and since 2007 has provided free MMC services in Rakai District. However, despite wide dissemination of information on the health benefits of MMC and free service provision, uptake in RCCS communities remains suboptimal (35% coverage among non-Muslim men in 2013). Research on determinants of MMC uptake is urgently needed for demand creation and targeted service provision. Using RCCS data, this study will identify individual sociodemographic, behavioral and psychosocial predictors of MMC acceptance; and by adding a new survey module to the RCCS 2015 surveys, the study will identify interpersonal and community level predictors of MMC uptake. Additionally, qualitative in-depth interviews and focus group discussions with men will be conducted to elucidate reasons why certain men do or do not accept MC. The quantitative evidence, augmented by the qualitative observations, will serve as the basis for an R21/01 to develop targeted strategies to increase MMC uptake and enhance the population level impact of MMC. Combining with the candidate's existing quantitative skills, the training in behavioral science theories and introduction to qualitative methods will help the candidate to establish an independent career in promoting health behaviors associated with a broad range of HIV preventive interventions (e.g. MMC, ART, pre-ART HIV care, PrEP and PMTCT).